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Date:   Fri, 14 Feb 2020 11:11:35 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Coly Li <colyli@...e.de>, kbuild test robot <lkp@...el.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>,
        linux-bcache@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 240/252] bcache: explicity type cast in bset_bkey_last()

From: Coly Li <colyli@...e.de>

[ Upstream commit 7c02b0055f774ed9afb6e1c7724f33bf148ffdc0 ]

In bset.h, macro bset_bkey_last() is defined as,
    bkey_idx((struct bkey *) (i)->d, (i)->keys)

Parameter i can be variable type of data structure, the macro always
works once the type of struct i has member 'd' and 'keys'.

bset_bkey_last() is also used in macro csum_set() to calculate the
checksum of a on-disk data structure. When csum_set() is used to
calculate checksum of on-disk bcache super block, the parameter 'i'
data type is struct cache_sb_disk. Inside struct cache_sb_disk (also in
struct cache_sb) the member keys is __u16 type. But bkey_idx() expects
unsigned int (a 32bit width), so there is problem when sending
parameters via stack to call bkey_idx().

Sparse tool from Intel 0day kbuild system reports this incompatible
problem. bkey_idx() is part of user space API, so the simplest fix is
to cast the (i)->keys to unsigned int type in macro bset_bkey_last().

Reported-by: kbuild test robot <lkp@...el.com>
Signed-off-by: Coly Li <colyli@...e.de>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/md/bcache/bset.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/bset.h b/drivers/md/bcache/bset.h
index c71365e7c1fac..a50dcfda656f5 100644
--- a/drivers/md/bcache/bset.h
+++ b/drivers/md/bcache/bset.h
@@ -397,7 +397,8 @@ void bch_btree_keys_stats(struct btree_keys *b, struct bset_stats *state);
 
 /* Bkey utility code */
 
-#define bset_bkey_last(i)	bkey_idx((struct bkey *) (i)->d, (i)->keys)
+#define bset_bkey_last(i)	bkey_idx((struct bkey *) (i)->d, \
+					 (unsigned int)(i)->keys)
 
 static inline struct bkey *bset_bkey_idx(struct bset *i, unsigned int idx)
 {
-- 
2.20.1

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